1. Field of the Invention
The present invention relates to a downstream processing of alkylate from low molecular weight olefin-isoparaffin polymerization using a sulfuric acid catalyst promoted with an anionic type surface active agent. More particularly, the present invention provides an improvement in downstream processing of gasoline production from alkylation using sulfuric acid.
2. Description of the Prior Art
Alkylation, in its broadest meaning, can be described as the addition or insertion of an alkyl group into a molecule. These alkylation reactions are diverse in nature and there is no inclusive or universal method of conducting alkylations. Each alkylation reaction is subject to its particular requirements as to free energy change, equilibrium, heat of reaction, equipment, catalyst, etc.
In the petroleum industry, the term alkylation is used in a more restricted sense to describe the addition of a low molecular weight hydrocarbon containing a tertiary hydrogen to an olefin to produce highly branched chain paraffins mainly in the C.sub.7 -C.sub.9 range which are high quality fuels for ignition engines. In commercial processes of this type, concentrated sulfuric acid and hydrofluoric acid are used.
In the case of these sulfuric acid alkylation processes, it has been shown that the addition of certain materials can result in improvements to the process. As examples: U.S. Pat. No. 2,276,251 teaches the use of organic bases such as amides, amines, imides, imines, pyridines, picolines, lutidenes, and collidenes; U.S. Pat. No. 2,375,637 teaches sulfur, selenium, tellurim, salts of condensation products of halogenated chlorosulfonic acids with amides of fatty acids, salts of amides, substituted amides of fatty acids, and salts of the sulfuric acid ester of aliphatic alcohols; U.S. Pat. No. 3,364,280 teaches surface active sulfonium or phosphonium salts; U.S. Pat. No. 3,231,633 teaches large, stable, surface-active cations; U.S. Pat. No. 3,551,514 discloses sodium stearate; U.S. Pat. No. 3,655,807 discloses dodecylbenzene sulfonic acid; U.S. Pat. No. 3,689,590 teaches p-Phenylenediamine; and U.S. Pat. No. 3,231,633 teaches triphenylmethylchloride, tetramethyl ammonium chloride, and trimethyl phosphonium chloride.
Many of the above suggested alkylation promoters are surface-active agents. For convenience, surface-active agents are classified as being anionic, cationic, non-ionic or amphoteric depending upon the actual or potential charge on the surface-active portion of the molecule. It is the chemical nature of anionic surface-active agents such as dodecylbenzene sulfonic acid, stearic acid, and sulfuric acid esters of aliphatic alcohols to partition between the acid and hydrocarbon phases in a sulfuric acid catalyzed alkylation process. As a consequence, the alkylate produced in processes using these promoters can be expected to contain some of the surface-active material in the alkylate itself.
An essential feature of practical sulfuric acid catalyzed alkylation processes is that the alkylate as produced should not contain trace quantities of sulfuric acid which can lead to severe corrosion problems downstream. In practice, alkylate is separated in a sulfuric acid catalyzed system by gravity. Under conditions normally employed, trace quantities of sulfuric acid remain in the alkylate. In order to elminate the downstream corrosion problems referred to, it is customary to neutralize or remove the acid by passing the alkylate through successive caustic scrub and water-wash steps. When using anionic-type surface-active promoters, the presence of these surface-active materials in the alkylate cause severe emulsification and interface problems so as to limit their practical utility. It is the purpose of this invention to describe a process in which these downstream operational problems are eliminated or minimized for alkylates containing trace quantities of anionic surface-active materials such as that produced by an anionic surface-active agent promoted sulfuric acid catalyzed alkylation process.